VIPER12-LED-EV STMicroelectronics, VIPER12-LED-EV Datasheet - Page 9

• Manufacturer Part Number: VIPER12-LED-EV
• Description: VIPER LED POWER SUPPLY
• Manufacturer: STMicroelectronics
• Series: VIPER™r

Specifications of VIPER12-LED-EV

• Mfg Application Notes: VIPower, AN1916 AppNote
• Current - Output / Channel: 350mA, 700mA, or 1.05A
• Outputs And Type: 1, Isolated
• Voltage - Output: 14V
• Features: Overvoltage Protection
• Voltage - Input: 90 ~ 264VAC
• Utilized Ic / Part: VIPer12A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q2105641

VIPER12A-E
6
Feedback pin principle of operation
A feedback pin controls the operation of the device. Unlike conventional PWM control
circuits which use a voltage input (the inverted input of an operational amplifier), the FB pin
is sensitive to current.
Figure 5.
The power MOSFET delivers a sense current I
R2 receives this current and the current coming from the FB pin. The voltage across R2 is
then compared to a fixed reference voltage of about 0.23 V. The MOSFET is switched off
when the following equation is reached:
By extracting I
Using the current sense ratio of the MOSFET G
Internal current control structure
S
:
Figure 5.
I
Doc ID 11977 Rev 2
D
presents the internal current mode structure.
=
R
G
2
ID
⋅
(
I
I
⋅
S
S
I
S
+
=
I
=
FB
0.23V
--------------- - I
R
G
)
2
ID
s
=
ID
which is proportional to the main current Id.
⋅
0.23V
–
⎛
⎝
:
0.23V
--------------- - I
FB
R
Feedback pin principle of operation
2
–
FB
⎞
⎠
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